Officially due for release tomorrow, the NZ COVID Tracer app is now available this evening for download on Apple's App Store and the Android Play Store.

A spokesperson from the Ministry of Health told 1 NEWS the app was submitted to the Google and Apple stores this evening, ready for the official launch at 6.30am tomorrow.

"There can be a wide variation in times between submitting apps and them going live. In this instance the processing time was efficient, and it is now live in both stores for New Zealanders to download."

Director-General of Health Dr Ashley Bloomfield will be appearing on TVNZ 1's Breakfast tomorrow at 7.10am to share details on the app launch.

Prime Minister Jacinda Ardern described it as a "digital diary" to help people keep track of where they've been and when.

It works by scanning QR codes on official NZ COVID Tracer posters.

The app says the data is kept securely on your phone and whenever the app is opened, data older than 31 days is automatically deleted.

The NZ COVID Tracer app.
Source: 1 NEWS

"It is intended to aid and support physical contact tracing efforts, not to replace them by any means," Ms Ardern said earlier this week.

"While there are other similar apps in this space, we wanted to give greater certainty about the use of the data that is collected, which this app happens to deliver."

To sign up, users need to supply an email address and a password, which is stored by the Ministry of Health using servers provided by Amazon in Sydney.

After that, all information is optional; the app recommends you give your full name and cellphone number, but it isn't required.

Screenshots from the official NZ COVID Tracer app.
Source: 1 NEWS

Users are also able to supply their birthday, gender, ethnicity and address, all optional.

In the app, the Ministry of Health says providing that extra detail can help make sure they contact the right person when multiple people share the same name.

It's not compulsory to sign up to the app and you're not legally obligated to release the tracking details stored on your device, according to the app's privacy policy.

It also says the data won't be shared with any other Government agencies unless they're directly involved with Covid-19 tracing efforts.